Materials Around Us

Hello my dear students! Welcome to today's science class. I am so happy to see all of you here. I hope you had a wonderful summer break and are ready to learn something new and exciting today. Today, we are going to start a brand new chapter from your NCERT Science book. The chapter is called "Materials Around Us". This is Chapter 6, and I promise you, by the end of this lesson, you will start looking at the things around you in a completely different way. You will start wondering, "What is this made of?" and "Why is it made of this particular material?" So let's begin our journey into the world of materials!

So students, let's start by thinking about what you brought to school today. Just look around your classroom. You have your notebook, your pen, maybe a water bottle, your school bag, and many other things. Now, think about this - all these objects that you see around you are made up of something, aren't they? Your notebook is made of paper. Your pen might be made of plastic and metal. Your water bottle might be made of plastic or glass. Your table is made of wood or metal. Your chalk is made of chalk powder. So basically, students, anything that is used to create an object is what we call a "material". That is a very important definition to remember. A material is any substance that is used to make an object.

Now, let's do a very interesting activity. I want you to look around your classroom and make a list of objects you see, and also write down what materials they are made of. This is Activity 6.1 from your book. You can make a table with two columns - in the first column, write what you observe, and in the second column, write the material it is made up of. For example, if you see a blackboard, it is made of wood and paint. If you see a glass window, it is made of glass. If you see your bench, it might be made of wood and metal. If you see a steel tumbler, it is made of metal called stainless steel. If you see a cloth duster, it is made of cloth or cotton. Try to list as many objects as you can. This activity will help you realize that we are surrounded by so many different materials!

Now, students, did you know that the earliest pottery found in the Indian subcontinent dates back to 7,000 to 8,000 years? It was found in the Ganga plains, in a place called Lahuradewa, and also in Baluchistan, in a place called Mehrgarh. Imagine, people were making pottery and clay objects thousands of years ago! Later, around 4000 BCE, during the Sindhu-Sarasvati civilization, which is also known as the Harappan civilization, people became very skilled at making pottery. They used wheels to turn the clay, they painted beautiful designs on the pots, and they baked the clay in special ovens called kilns. The baked clay is called "terracotta". These pots were used for cooking food, storing grains, oil, and ghee. Some of these beautiful pottery items are even displayed in the National Museum in New Delhi. So you see, students, materials have been an important part of human civilization for thousands of years!

Now, let's move to the next section of our chapter. We are going to learn about how to group materials. This is a very important concept called "classification". Let me explain what classification means.

So students, let's say you have a basket full of different fruits - apples, bananas, oranges, grapes, and mangoes. How would you arrange them? You might put all the fruits together, or you might group them by their color, or by their size, or by whether they have seeds or not. Similarly, in your kitchen, you keep all the spices together, all the pulses and grains together, and all the utensils together. This is exactly what classification is! Classification is the method of arranging objects into groups based on some common property that they share. Objects can be classified on the basis of their shape, color, hardness, softness, shine, dullness, or the material they are made up of.

Now, let's do Activity 6.2. Look at Figure 6.1 in your book, which shows various objects around us. Try to group these objects based on any common property. For example, you could group all round objects together, or all objects made of metal together, or all objects that are hard together. There is no right or wrong answer here. The important thing is that you are thinking about how these objects are similar or different.

Now, after you have grouped the objects, think about these questions: Which property did you use to group the objects? Did your friends group objects based on similar properties? What did you learn from this activity? You must have noticed that an object can be made from different materials, and some materials can be used to make more than one object. For example, a chair can be made of wood, or metal, or plastic. Similarly, plastic can be used to make a pen, a bottle, a bag, and many other things. This is a very important observation, students!

Now, let's do Activity 6.3. Think about what materials we can use to make a tumbler. A tumbler is something you drink water from. Look at Figure 6.2 in your book. What materials can we use to make a tumbler? We could use glass, plastic, metal, clay, and so on. Now, think about this question: Would it be a good idea to use paper-like materials for making cooking utensils? No, of course not! Because paper-like materials would catch fire when heated, and they would not be able to hold hot food or water. Another question: Why cannot a tumbler made of cloth be used for storing water? Because cloth absorbs water and lets it pass through! So the materials that are required to make a tumbler should be capable of holding water. This is very important, students!

Now, let me ask you a very important question: What decides which material should be used for making an object? The answer is - we choose a material depending on its properties and the purpose for which the object is to be used. For example, we use different materials for making different parts of a pen. The body of the pen might be made of plastic, the tip might be made of metal, and the ink inside is made of various chemicals. Each material is chosen because of its specific properties that make it suitable for that particular part.

Now, think about this question: Why are different materials used for making balls for various sports? Can a cricket ball be used to play tennis? No! A cricket ball is hard and heavy, suitable for hitting with a bat. A tennis ball is softer and bouncier, suitable for hitting with a racket. A football is made of leather or synthetic material and is inflated with air. Each ball is made of a specific material because of the specific requirements of that sport. This is a perfect example of why we need to choose the right material for the right purpose!

Now, let's do Activity 6.4. Look at Figure 6.3, which shows a variety of balls that are of the same size but made up of different materials. Take each ball and drop it from a fixed height. Note the height to which the ball bounces and record it in Table 6.2. Identify the ball that achieves the highest bounce. You might have a tennis ball, a cricket ball, a hand exercise ball, and maybe a rubber ball. Each ball will bounce differently because they are made of different materials with different properties. After doing this activity, discuss in class other properties of sports balls, such as their size, color, texture, and how high they bounce. This will help you understand why balls are made up of specific materials for specific sports.

Now, look at Figure 6.4 in your book. Try to group the objects in as many different ways as possible. You might group them according to their shapes, or by their color, or by the materials they are made up of. This is another exercise in classification.

So, what have we learned so far, students? We have learned that materials may be classified on the basis of their properties. Classification helps us study and observe patterns in the properties of things. Humans have been classifying not only things, but also rocks, plants, and animals. You might have learned about the classification of living things in your biology chapters. Similarly, classification of non-living things is also done on the basis of their properties. This is exactly what we are doing in this chapter!

Now, let's move to a very interesting part of our chapter - we are going to learn about the different properties of materials. This is Section 6.3. So students, let's explore the various properties that materials can have!

The first property we are going to learn about is the appearance of materials. Materials often look different from each other. Freshly cut wood, which is unpolished, has a distinct appearance, quite different from that of iron. Similarly, iron looks different from copper or aluminium. However, there might be some similarities among iron, copper, and aluminium that make them different from wood. What could that be? Let's find out!

Let me give you a sorting challenge! Collect small pieces of paper, cardboard, wood, chalk, copper wire, aluminium foil, and any article made up of brass, bronze, steel, and so on. Take a look at the pieces you have collected. Do any of these materials shine when light falls on them? Observe their texture - whether they are rough or smooth - their color, and other noticeable features. Now, group the collected pieces based on their appearance.

Students, materials that typically have shiny surfaces are said to have a "lustrous" appearance. Such materials with lustre are usually metals. Examples of metals include iron, copper, zinc, aluminium, gold, and so on. However, some metals may lose their lustre and start to look dull or non-lustrous due to the effect of air and moisture on them. As a result, we often notice the lustre only on their freshly cut surfaces. Non-lustrous materials are those that do not have a shiny surface. Some examples of non-lustrous materials are paper, wood, rubber, jute, and so on.

Now, there is an old saying: "All that glitters is not gold!" This means that not all the materials that shine are metals. Surfaces of some materials are made shiny by polishing or coating them with thin layers of plastic, wax, or any other material which makes them look shiny. These materials may not be metals. So be careful, students! Just because something looks shiny doesn't mean it is a metal!

Now, let's learn about another property - whether materials are hard or soft. When you press different objects or materials with your hands, some of them like stones may be hard to compress, while others like an eraser can be easily compressed. Take a metal key and use it to scratch the surface of a piece of wood, aluminium, stone, iron, candle, chalk, and any other material or object. Can some materials be scratched more easily than others? Materials which can be compressed or scratched easily are "soft", while other materials which are difficult to compress or scratch are "hard". However, these properties are relative in nature. For example, rubber is harder than sponge but softer than iron. So, students, hardness and softness are not absolute properties - they are relative. What feels hard to you might feel soft to someone else, or compared to another material!

Now, let's do Activity 6.5. Hold the objects given in Table 6.3 with your hands. Feel whether the objects are hard or soft. Find out the materials they are made up of. Enter your observations in Table 6.3. The table has objects like brick, water bottle, pillow, tumbler, table, sweater, and any other object you want to add. For example, a brick is hard and is made of baked clay. A water bottle might be hard and made of plastic. A pillow is soft and made of cloth and filled with cotton or foam. A tumbler might be hard and made of glass or metal. A table is hard and made of wood or metal. A sweater is soft and made of wool or cotton. Compare your observations with the observations of your friends and discuss. This will help you understand that different materials have different hardness or softness.

So, what have we learned so far, students? We have learned that materials can have different properties, like lustre, hardness, softness, and color. But can you think of any other properties that are shown by materials? Let us explore it further!

Now, let's learn about another very interesting property - whether we can see through materials or not. Let me tell you a story. Ghulan, Sheeta, and Sara are playing hide and seek with their friends. Ghulan hides behind a wall, Sheeta hides behind a big tree in the garden, while Sara hides behind the frosted glass door, which has a hazy surface. Sheeta's younger brother can see all of this happening through a glass window of his house.

Now, think about this: Why did Ghulan, Sheeta, and Sara choose these places to hide? They chose these places because they thought they would not be seen! But was that true? Let's find out!

The materials through which things can be seen clearly are called "transparent". Glass, water, air, cellophane paper, and so on are some examples of transparent materials. So, if Sheeta's brother was looking through a clear glass window, he could see everything clearly!

Now, do you think it would be possible for Sheeta's brother to see her and her friends through a closed wooden window of the house? No! Because wood is not transparent. There are many materials through which you are not able to see at all. These materials are called "opaque". Wood, cardboard, and metals are examples of opaque materials.

Now, what about the frosted glass that Sara used to hide behind? The materials through which objects can be seen, but not clearly, are known as "translucent". Butter paper and frosted glass are examples of translucent materials. So, through frosted glass, you can see that someone is there, but you cannot see them clearly!

Now, look at Figure 6.5 in your book. Identify and label the nature of materials used by Ghulan, Sheeta, Sara, and Sheeta's brother. Ghulan hid behind a wall - what kind of material is a wall made of? It is probably made of brick or concrete, which is opaque. Sheeta hid behind a big tree - a tree trunk is also opaque. Sara hid behind a frosted glass door - that is translucent. Sheeta's brother was looking through a glass window - that is transparent. So the answers would be: A is opaque, B is opaque, C is translucent, and D is transparent.

Now, let's do Activity 6.6. Classify the following objects as transparent, translucent, or opaque in Table 6.4. The objects are: glass tumbler, butter paper, eraser, frosted glass, wooden board, and window glass. A glass tumbler is transparent. Butter paper is translucent. An eraser is opaque. Frosted glass is translucent. A wooden board is opaque. Window glass is transparent. Very simple, isn't it?

Now, let's learn about another property - whether materials dissolve in water or not. Let me tell you another story. Ghulan was sweating when he came home after playing in the evening. He was feeling tired and thirsty. Ghulan's mother mixed a spoonful of sugar, a pinch of salt, and some lemon juice in a glass tumbler of water and offered him this "shikanji" or lemonade to drink. Ghulan noticed that while his mother was mixing sugar and salt in water, the salt and the sugar disappeared after a while. Have you ever noticed this? When you add sugar to water and stir, the sugar seems to disappear. But actually, it doesn't disappear - it dissolves in the water. The sugar molecules spread out evenly throughout the water, so we cannot see them anymore.

Now, let's do a simple activity to explore how different materials behave when we mix them in water! This is Activity 6.7. Collect small amounts of sugar, salt, chalk powder, sand, and sawdust. Take five glass tumblers and fill them about two-thirds with water. Put a teaspoonful of sugar in the first glass tumbler, salt in the second one, chalk powder in the third, sand in the fourth, and sawdust in the fifth glass tumbler. On stirring, predict what will happen in each case. Then use a spoon to stir well the contents of each glass tumbler. Wait for a few minutes and watch what happens. Write down your observations in Table 6.5.

Now, what do you think will happen? For sugar - it will disappear in water, meaning it will dissolve. For salt - it will also dissolve in water. For chalk powder - it will not dissolve; it will just settle at the bottom. For sand - it will also not dissolve; it will settle at the bottom. For sawdust - it will float on top and will not dissolve. So, students, some materials completely disappear when mixed in water. We say that these materials "dissolve" in water, or in other words, they are "soluble" in water. Some materials do not mix with water and do not disappear even after we stir them for a long time. These materials are "insoluble" in water.

Water plays an important role in the functioning of our body because it can dissolve a large number of materials. That is why it is so important for us to drink water!

Now, I want to tell you something very useful. Do you know what ORS is? ORS stands for Oral Rehydration Solution. It is used to treat dehydration due to diarrhoea or other illnesses. These ready-made ORS packets are available in primary health centres and also in the market. Each packet is dissolved in a litre of water before use. If these are not available, ORS can be prepared at home by mixing six teaspoons of sugar and half a teaspoon of common salt in one litre of boiled and cooled water. This is a very important home remedy, students! So you see how solubility is important in our daily life!

Now, some liquids get completely mixed with water. Some do not mix with water and form a separate layer when left undisturbed for some time. Similarly, some gases are soluble in water, whereas others are not. For example, oxygen gas dissolves in water. It is very important for the survival of animals and plants that live in water. That is why fish can breathe in water - because oxygen is dissolved in it!

Now, let's learn about another property - how heavy or light materials are. This is about mass. Let's do Activity 6.8. Take three identical paper cups or bowls. Fill each cup half with the provided materials. Fill one with water and mark it as 'A', the second with sand and mark it as 'B', and the third with pebbles and mark it as 'C'. Predict which one would be heavier and which one would be lighter. Then, weigh each cup using a balance and record the readings in your notebook. Compare the data and infer which is heavier or lighter.

From this activity, we can say that any object which is heavier or lighter can be measured in terms of a property called "mass". The one which is heavier has more mass, and the one which is lighter has less mass. Now, students, I want you to remember that weight is sometimes used in common language for mass, as it is determined by weighing. You will learn more about mass and weight and their relation in higher classes. For now, just remember that mass is the amount of matter in an object.

Now, let's talk about space and volume. The next day, Madam Vidya enters the class. All the students stand up to greet her. She reciprocates and deliberately says, "Please keep your bags on your seats and sit down." Students are not able to sit because bags are kept on their seats. Madam Vidya asks, "Why are you not sitting?" The students reply that there is no place to sit because the bags have occupied that space.

This is a perfect example to understand volume! Continuing the conversation, she provides two identical glass tumblers to two students and encourages them to pour the remaining water from their drinking water bottles into the respective glass tumblers. On pouring water in the glass tumblers, the students observe that one glass tumbler gets half-filled with water while the other is almost completely filled with water. Why is the level of water different in the two tumblers?

Madam Vidya elaborates that both tumblers have the same capacity. The water levels differ in each case, which indicates that the amount of water in each tumbler is different. The water in the first tumbler occupies less space, indicating that the volume of water in this tumbler is less than the water in the other tumbler. The space occupied by water represents its "volume". So, students, volume is the amount of space that a substance or an object occupies.

Now, think about this: Why was I not able to transfer water from the jug into an empty water bottle completely? Now I know the reason behind it! The reason is that the bottle was already full - it had no more volume to hold more water!

You may have noticed drinking water bottles of different sizes being sold in the market. Have you noticed 1 L, 500 mL, 200 mL, and so on written as net quantity on the bottles? These indicate the volume of water in the bottles. The bottles of drinking water and milk are labelled as 500 mL, indicating the volume. So, volume is measured in litres and millilitres.

Now, let's learn about the units of mass and volume. The SI unit of mass is kilogram, abbreviated as kg. There is no space between 'k' and 'g' in kg, and no full stop after the symbol, except at the end of a sentence. While writing the mass, always leave a space between the number and the unit. For example, if we have a mass of 7 kilograms, it would be written as 7 kg, not as 7 kgs. Similarly, litre is abbreviated as capital L, and millilitre as mL. There is no space between 'm' and 'L' in mL. For example, if you have 500 millilitres of water, it would be written as 500 mL, with m in lower case and L in upper case. The SI unit for volume is cubic metre, abbreviated as m³. The abbreviation is written with a superscript 3 to denote cubic metre. For example, if you have a volume of 2 cubic metres, it would be written as 2 m³. Always leave a space between the number and the unit. And remember, 1 m³ equals 1000 L.

Now, students, we have learned about many properties of materials. But are there any properties which can be shown by all materials? Let me ask you this question: What do all materials have in common? Can you think about it?

Mass and volume are the two properties that are possessed by all materials. Can we give a general name to anything that possesses these two properties? Yes! Anything that occupies space and has mass is called "matter". The mass gives the quantity of matter, and the units to measure it are gram and kilogram. The space occupied by matter is its volume, and the units to measure it are litre and millilitre.

So, students, now you know what matter is! Matter is anything that has mass and occupies space. Water is matter. Sand and pebbles are matter. The cup you drink from is matter. Air is also matter! Can all the materials around us be considered as different examples of matter? Yes! Materials are types of matter used in the creation or making of objects.

Now, let's think about something interesting. Can you think about what changes the invention of plastic brought to humans? Is it a boon or a bane? Plastic is a material that is cheap, durable, and can be molded into any shape. It has revolutionized packaging, construction, and many other industries. However, plastic is also a major pollutant and takes hundreds of years to decompose. So, it is both a boon and a bane! We need to use plastic responsibly and try to recycle it whenever possible.

Now, I want to tell you something fascinating. A similar classification system existed in ancient India. Ayurveda, one of the Indian medical systems, also has a system of grouping things. There is a shloka, which is a verse in Sanskrit, that talks about 20 properties, which are used to describe all physical matter in Ayurveda. These properties can also be used to describe all living systems - plants, animals, and humans - the environment, and also food. These properties include heavy versus light, slow versus quick, cold versus hot, oily versus dry, smooth versus rough, solid versus liquid, soft versus hard, stable versus moving, subtle versus big, and non-slimy versus slimy. Isn't that amazing, students? Our ancestors were also doing classification thousands of years ago!

Now, let's go through the keywords of this chapter. The keywords are: classification, non-lustrous, classify, hard, opaque, explore, insoluble, soft, lustrous, soluble, mass, material, matter, translucent, transparent, predict, record, volume, and so on. Make sure you understand the meaning of each of these words.

Now, let's solve the exercises in your book. First, let's do "Let us play" - Find the companion. Link the following words by putting arrows between words that have a connection. The table shows: Iron, Transparent, Solid, Plastic, Wood, Glass. And the other column has: Copper, Bottle, Lustrous, Opaque. So, we need to connect iron with lustrous, because iron is a metal and metals are lustrous. Transparent should be connected with glass, because glass is transparent. Solid should be connected with plastic, because plastic can be solid. And wood should be connected with opaque, because wood is opaque. The remaining ones: Copper should be connected with lustrous, because copper is a metal and is lustrous. Bottle should be connected with plastic, because bottles are often made of plastic. So the connections are: Iron to Lustrous, Transparent to Glass, Solid to Plastic, Wood to Opaque. And also: Copper to Lustrous, Bottle to Plastic.

Now, let's do "Win the Word-hub" game. This is a game where you randomly choose nine words from the given list - lustrous, non-lustrous, soluble, insoluble, hard, soft, matter, mass, transparent, opaque, volume, and translucent - and write them in a grid. Then, the facilitator either reads the definition of a word or the word itself, and the learners have to tick if the particular word is there in the grid. Whoever finishes ticking off all nine words first will shout out "Hurray!" That person will be the winner if his or her words are marked correctly. This is a fun game to reinforce the vocabulary of the chapter!

Now, let's do "Let us enhance our learning" - the exercises. Exercise 1: Visit your kitchen and observe how your parents have organized various edibles. Can you suggest a better sorting method? Write it in your notebook. Think about how your parents keep things in the kitchen - maybe they keep all the spices together, all the pulses and grains together, all the oils and sauces together, and so on. You could suggest a better sorting method, like grouping by type - all raw foods together, all cooked foods together, or grouping by how they need to be stored - things that need refrigeration versus things that can be stored at room temperature.

Exercise 2: Unscramble the letters in Column I and match with their properties in Column II. Column I has: (i) T R E M A T, (ii) U L S B E L O, (iii) T N E R P A S N A R T, (iv) E R U S T L. Let's unscramble these: T R E M A T is MATTER. U L S B E L O is SOLUBLE. T N E R P A S N A R T is TRANSPARENT. E R U S T L is LUSTRE. Now, let's match with Column II: (a) Objects can be seen clearly through it - this is TRANSPARENT. (b) Occupies space and has mass - this is MATTER. (c) Shiny surface - this is LUSTRE. (d) Mixes completely in water - this is SOLUBLE. So the matches are: (i) with (b), (ii) with (d), (iii) with (a), (iv) with (c).

Exercise 3: The containers which are used to store materials in shops and at home are usually transparent. Give your reasons for this. Why are containers transparent? Because we can see what is inside without opening them! This helps us know how much quantity is left, whether the item is fresh or spoiled, and so on. Transparent containers make it easy to find things quickly.

Exercise 4: State whether the statements given below are True or False. Correct the False statements. (i) Wood is translucent while glass is opaque. This is FALSE. Wood is opaque, and glass is transparent. So the correct statement is: Wood is opaque while glass is transparent. (ii) Aluminium foil has lustre while an eraser does not. This is TRUE. Aluminium foil is a metal and has lustre, while an eraser is made of rubber and does not have lustre. (iii) Sugar dissolves in water whereas sawdust does not. This is TRUE. Sugar is soluble in water, while sawdust is insoluble. (iv) An apple is a matter because it occupies no space and has mass. This is FALSE. An apple does occupy space and has mass, so it is matter. The correct statement is: An apple is matter because it occupies space and has mass.

Exercise 5: We see chairs made up of various materials, such as wood, iron, plastic, bamboo, cement, and stones. Following are some desirable properties of materials which can be used to make chairs. Which materials used to make chairs fulfil these properties the most? (i) Hardness - does not bend or shake on sitting even after long use. A chair made of cement or stone would be very hard and durable. Iron chairs are also hard. (ii) Lightweight - easy to lift or to take from one place to another. Bamboo chairs and plastic chairs are lightweight. (iii) Does not feel very cold when sitting during winters. Wood and plastic do not feel as cold as metal or stone. (iv) Can be cleaned regularly and made to look new even after long use. Plastic and metal chairs can be cleaned easily and can be made to look new.

Exercise 6: You need to have containers for collection of: (i) food waste, (ii) broken glass, and (iii) wastepaper. Which materials will you choose for containers of these types of waste? What properties of materials do you need to think of? For food waste, we need a container that is waterproof and easy to clean - maybe plastic or metal. For broken glass, we need a container that is strong and will not let the sharp edges cut through - maybe a cardboard box or a plastic container. For wastepaper, we need a container that is open at the top and can hold paper - maybe a cardboard box or a plastic bin. The properties we need to think of are: strength, durability, water resistance, and ease of cleaning.

Exercise 7: Air is all around us but does not hinder us from seeing each other. Whereas, if a wooden door comes in between, we cannot see each other. It is because air is _______________ and the wooden door is _______________. Choose the most appropriate option: (i) transparent, opaque; (ii) translucent, transparent; (iii) opaque, translucent; (iv) transparent, translucent. The correct answer is (i) transparent, opaque. Air is transparent, and wood is opaque.

Exercise 8: Imagine you have two mysterious materials, X and Y. When you try to press material X, it feels rigid and does not change its shape easily. On the other hand, material Y easily changes its shape when you press it. Now, when you mix both materials in water, only material X dissolves completely, while material Y remains unchanged. What can materials X and Y be? Can you identify whether material X is hard or soft? What about material Y? Justify your answer. Material X feels rigid and does not change its shape easily - so it is hard. But it dissolves in water - so it must be something like sugar or salt, which are hard crystals but soluble in water. Material Y easily changes its shape when pressed - so it is soft. And it does not dissolve in water - so it must be something like sand or chalk powder, which are insoluble. So, material X is hard and soluble, like sugar or salt. Material Y is soft and insoluble, like sand or chalk powder.

Exercise 9: (i) Who am I? Identify me on the basis of the given properties. (a) I have lustre. The answer is a metal, like iron or copper. (b) I can be easily compressed. The answer is something soft, like a sponge or cotton. (c) I am hard and soluble in water. The answer is something like sugar or salt. (d) You cannot see clearly through me. The answer is translucent or opaque material, like frosted glass or wood. (e) I have mass and volume but you cannot see me. The answer is air or any gas!

Exercise 9: (ii) Make your own 'Who am I?' This is a fun activity where you create your own riddles about materials based on their properties. Try to make at least five such riddles!

Exercise 10: You are provided with the following materials - vinegar, honey, mustard oil, water, glucose, and wheat flour. Make any two pairs of materials where one material is soluble in the other. Now, make two pairs of materials where one material remains insoluble in the other material. For soluble pairs: glucose dissolves in water, and honey dissolves in water. For insoluble pairs: wheat flour does not dissolve in water, and mustard oil does not dissolve in water (it forms a separate layer).

Now, let's do "Learning further". Gather information on different materials which can be recycled. You can take help from various sources, such as newspapers, magazines, elders in your community, and the internet. Recyclers buy old objects based on properties of the materials and do not bother even if an object is broken. Conduct a survey with recyclers near you and find out what properties of materials do they check before buying objects from households. Which materials do they not buy and why? Collect 20 to 30 objects from your household and classify them based on the properties of the materials they are made up of. Were you able to put them in separate groups? What relationship do you see between the properties of the materials and the use of the objects? Create and decorate a useful object of your choice using discarded materials and bring it to the class. Discuss with your friends what they have made and the materials they have used. Additionally, provide constructive feedback on areas for improvement, considering functionality and any other points.

Now, students, we have come to the end of our lesson. Let me give you a complete summary of everything we have learned in this chapter.

In this chapter, we learned that objects are made from a large variety of materials. An object can be made up of a single material or a combination of different materials. We can use different materials to make objects with similar functions. The method of arranging objects into groups is called classification. Materials possess different properties which determine their use. Materials are grouped or classified based on their similarities or differences in their properties.

We learned that materials can be grouped based on appearance, such as lustrous or non-lustrous. Lustrous materials have a shiny surface and are usually metals, while non-lustrous materials do not have a shiny surface. Materials are also grouped based on the feel, such as hard or soft. Hard materials are difficult to compress or scratch, while soft materials can be easily compressed or scratched. However, these properties are relative in nature.

Materials are grouped as transparent, translucent, or opaque, depending on how much we can see through them. Transparent materials allow us to see clearly through them, like glass and water. Translucent materials allow us to see objects but not clearly, like frosted glass and butter paper. Opaque materials do not allow us to see through them at all, like wood and metal.

Some materials are soluble in water, while others remain insoluble. Soluble materials dissolve completely in water, like sugar and salt. Insoluble materials do not dissolve in water, like sand and chalk powder.

Anything that occupies space and has mass is called matter. The space occupied by matter is its volume. Mass quantifies the amount of matter present in an object. The SI unit of mass is kilogram, and the SI unit of volume is litre or cubic metre.

We also learned about the historical significance of materials, like the ancient pottery in India, and the classification system in Ayurveda. We learned that classification is a useful tool that helps us study and observe patterns in the properties of things.

So, students, I hope you have enjoyed this lesson and learned a lot about the materials around us. Remember to look around you and think about what materials things are made of and why those materials are used. This will help you understand the world better!

Thank you for listening attentively. See you in the next class!